VHF Antenna lengths

[bigeasy1]

I've always run 8' Shakespeare Galaxy vhf atennas on all my previous boats,mostly mounted on the gunnels or side of the hardtop.
For those of you with center consoles with T-Tops,what length antennas are you running?

The reason for the question,is that I installed an arch on my Tsunami,and wonder if because of the tower height(approx 76"above the deck)if i can get away with a shorter one,and still get good range from it.

I'm a bit concerned about mounting an 8' on top of the arch,only because when i trailer it there won't be a lot of support for it when it's laid down horizontally.

The arch is about 30" wide,so there would be at least 6' hanging unsupported.There will be one long trip of 400 miles,to where It will live,then,once it's there, only about a mile to the launch thereafter.

Just wondering what kind of reception i can get from,say,a four foot model.
Any comments would be helpful,Thanks all.